How electroless nickel differs

Electroless nickel is deposited by a chemical reaction in the bath, not by an electric current. Because there is no current, the coating does not build up on edges and thin out in holes. Bores, threads, slots and recesses get close to the same thickness as flat faces. That makes it the usual choice for machined parts with tight tolerances and for complex shapes.

The coating is an alloy of nickel and phosphorus. The phosphorus content changes its properties, so ASTM B733 groups electroless nickel by phosphorus range.

Mid or high phosphorus

	Mid-phosphorus	High-phosphorus
Phosphorus	5–9% (ASTM B733 Type IV)	10% and above (ASTM B733 Type V)
Appearance	Bright to semi-bright	Semi-bright
Corrosion resistance	Good	Best, especially in acidic conditions
Magnetic	Slightly magnetic	Non-magnetic as plated
Typical use	General engineering, wear surfaces	Corrosive environments, RF and electronic parts that must be non-magnetic

Hardness and adhesion

As plated, electroless nickel is already harder than electroplated nickel. Some drawings call for a bake after plating to raise the hardness further. We do not offer this, so parts are supplied with the as-plated hardness. If your drawing calls for a hardness bake, tell us in your enquiry.

Adhesion is checked by thermal shock: plated parts are heated and then quenched in cold water, and the coating must not blister or flake.

On aluminium

Aluminium needs a zincate pre-treatment before electroless nickel so that the coating bonds properly. Electroless nickel is widely used on aluminium RF filter housings, lids and machined enclosures, often as a base for silver. See electroless nickel plating on aluminium for the choice of phosphorus, tolerances and what to send, and plating on aluminium for how aluminium parts are prepared.

What to put on your drawing or enquiry

Base material and grade, including the aluminium alloy
Mid or high phosphorus, or the ASTM B733 type
Thickness in µm, and any surfaces that must stay uncoated
Any hardness or heat-treatment requirement
The plating specification and revision, if you work to one
Quantity per lot and expected yearly volume

Specifications

We plate electroless nickel to ASTM B733, the standard for autocatalytic nickel-phosphorus coatings. A full callout gives the type (phosphorus range), service condition (thickness for the environment) and class (heat treatment).

Specification	What it covers
ISO 4527	International standard for autocatalytic (electroless) nickel-phosphorus coatings.
SAE AMS 2404	Electroless nickel plating, used on aerospace drawings.
AMS-C-26074	Electroless nickel coatings, the SAE version of the former military specification MIL-C-26074.

Send the specification and revision with your drawing and we will confirm whether we can meet it.